Add Pajamas-compliant empty state to `app/views/projects/no_repo.html.haml`
The `app/views/projects/no_repo.html.haml` template is rendered when a project exists without any source code (repository).
We could use the [Pajamas-compliant empty state](https://design.gitlab.com/regions/empty-states#fallback) here in place of the current implementation:

issue